The best way to set material/model HDPE plate?
1- You should model it, this is called beveling (bevel modifier or CTRL+B with edge selected)

2- Through texture is the best way, either with face loops and face assigning different material or with one material for the whole mesh and a node system with gradients, mapping node, and very contrasted ramps.

This is a cool project and an easy model but you'll have some trouble if you don't study subdivision surface modeling and some common modifiers (solidify, bevel, mirror...). This is typically a 'hard surface' model, might want to do some googling with theses key terms to learn a bit more about modeling in Blender. For more specific questions stack exchange will be there for you though :)